02 November 2011

I wrote this some time back after reading Tom Murphy's blog. I'll publish this as is because it is still worth saying even though it is really more shallow than I wanted.

I was reading Tom Murphy's blog, Do The Math, about the future of space flight. In a nutshell, it has no future. These are hard words for many people raised with the dream-become-expectation that people (usually American) will venture into space and colonise other worlds.

I sympathise. When I first realised that civilisation was in dire straits because: no we had not developed fusion; no we had not developed safe/cheap nuclear; no we had not developed a cheap replacement for petroleum and no we had not developed a better means of getting into space -- well I was not happy. In fact I found it deeply depressing, because even rudimentary calculations show that our current civilisation cannot continue as is. A relevant motto comes to mind: per ardua ad astra often translated as, "A rough road leads to the stars". You don't get
there by dreaming and you shouldn't let your expectations outrun your
dreams.

There is a lot of energy being thrown about in the universe. Nature likes to show off on the grand scale. Sadly we can only intercept a tiny fraction and then we have to cajole it, at cost, into another form that we can use. We can look longingly at the lakes of hydrocarbons on Titan or the vast energy output of a solar prominence but we can't tap it. Just as the people of the neolithic could not tap the hydro-power of a waterfall. But they could at least walk up to it, perhaps even dream of a water wheel. We cannot just walk up to these things.

Is there any future for Space Flight/Travel/Exploration? I don't know. The trouble is that it takes a lot of complex interacting industries to create and to support a spacecraft. It is Rocket Science after all. But when the global energy pie starts shrinking then the web of requirements needed to make a spaceship starts fraying and breaking and the reliability of a launch will suddenly drop to zero. Long before we get to that stage I think people in power, ie politicians, will start pointing out that there are other demands for the energy/materials that the launch requires.

Perhaps we could, after a rough patch, develop fusion and rebuild and head off to space again. Is that possible? At this point it is worth mentioning a simple equation from basic mechanics, it is the Rocket Equation:

basically you can see that you need lots of fuel but more importantly a high exhaust velocity for your rocket. In fact twice the exhaust velocity will give you twice the final velocity. You can play around with the values and get all sorts of interesting results. For example, if you have a rocket that can throw empty bits of rocket away you can reduce your final rocket mass value and therefore increase the velocity. This is the idea behind multi-stage rockets. Or instead you could have a high exhaust velocity. Well that is hard to do unless you have something like an ion drive which has high exhaust velocity but not many particles and hence not much thrust ... which means you have to have a small craft and run the engine for a long time. No-one said the final velocity was reached in short time. Good for small unmanned explorer craft. Chemical energy in conventional rockets can give us a lot of thrust but with a relatively low exhaust velocity. Ion rockets give high exhaust velocity but low thrust. It would be nice to have something else. Many authors have played with the idea of nuclear fusion as a method of generating power and propulsion on a spacecraft. Looking at some simple figures shows us why (the last column relates to the final velocity)

Exhaust Velocity (m/s)

Rocket Mass (kg)

Rocket Fuel (kg)

Days to Travel 100Mkm

Exhaust Temp K

1000

80000

50000

2384

80200

5000

80000

50000

477

2006450

10000

80000

50000

238

8020000

20000

80000

50000

119

32000000

30000

80000

50000

79

72000000

Notice that the exhaust temperature* rapidly goes into the millions of degrees. Here I am assuming a deuterium exhaust. A velocity over 10,000 m/s seems 'unrealistic' even considering we are in pure speculation mode.

Caveat: I have made no allowance for the huge gravity well of the solar system. Even with such fusion motors you would have to play it smart and not use wasteful 'direct' paths to destinations.

I don't see it happening, well not the way our society is at the moment. If we had cheap fusion ... well that is dreaming again. Waiting for the aliens to come and rescue us, or the secret government free-energy devices that have been suppressed. Yeah right. Might happen, I wouldn't like to bet my civilisation on it though.

So will humans ever venture into space again in a serious, sustained manner? I want to think so. But the only way I could see it happening is that humans build a civilisation that was frugal, innately curious and interested in knowledge and was very, very smart. I don't see that happening with Homo Sapiens. Fast forward 100,000 years. The CO2 in the atmosphere gets picked up by the carbon cycle. The natural climate re-asserts itself with the beginning of a new glacial period. Human populations contract, get pressured ... and pressured. A new interglacial starts with a new species of human. This is starting to sound a bit like Last and First Men by Olaf Stapledon.

Well that is all very depressing. Is there an alternative? The more we wish to go physically to a place the more it will cost. Manned spaceflight to Mars is horrendously expensive and the rewards are debatable; Unmanned spaceflight to Mars is somewhat expensive but the rewards are great; Remote observation of Mars is routinely done, inexpensive and often has surprising discoveries. Umanned exploration and remote observation may keep humanity's dream alive while some alternative is developed. Failing that, remote observation could fade into a deep tribal knowledge of the heavens that may survive to better times. Amazing successors to Stonehenge? Never forget that humans have studied the heavens for many thousands of years.

So where to now? I don't have any answers. Do you?

* Exhaust temperature is calculated by back of the envelope calculation using the V_rms in the Maxwell Speed Distribution equation.

25 June 2011

It has been almost a month since I last posted. Deary me, a bit slack. Well I have been reading and getting a little obsessive about the Oil Crisis. Most would say there is no crisis yet but you know it depends how you look at it. One interesting aspect of the human mind is that it allows us a kind of time-independent sense of things. We see the past, and we extrapolate to the future ... and we sense Time: past, present and future. This seems to be a pretty advanced kind of perception which may be unique to humans (Note: this kind of species arrogance has a bad track record) so perhaps it would be a good idea to actually use it. Our culture has become a willing slave of the Cult of Instant Gratification. We replace debate with sound bytes, essays with 140 characters of twitter 'wisdom'. We are letting our sense of Time atrophy by the narrowing of our sense of the Present.

Hollywood once gave us disturbing and motivating work, not just the light stuff. Now we seem to be deluged by fluff that has brainwashed us into thinking that tough problems are easily solved. That some small victory in a movie means everything is OK. And now, when we need to think clearly and far ahead, we are at our weakest. Many people are already waking from their American (or Australian or wherever) Dream to a harsh reality. It isn't really their fault, they didn't ask for it, they just worked hard and wanted some good things for themselves and their families. But the real world doesn't care about intentions it only cares about what happened. We have used too much energy too quickly it has acted like irrigation in the desert ... society and civilization bloomed ... but there was only so much water, when the pressure starts to drop the plants will wilt, the soil will get dusty. Flowers will no longer bloom and the oasis will start to stress. See this for an example.

Perhaps that is the analogy I have been looking for recently between our civilization and its dependency on oil: an ecosystem and its dependency on water. A rainforest is an amazing thing it creates its own weather and recycles water through itself. It conserves water and retains its integrity like an organism. When a drought occurs water levels drop in streams, then streams disappear. The density of the forest drops and some leaves etc are lost. Eventually trees start to die and the forest thins out. The forest is now very vulnerable. If a fire comes by it will sweep through the forest, destroying it and possibly enabling a different new permanent ecosystem. Not all of the forest will face this fate however because not all of the forest will suffer the same water levels. Some areas will be more blessed, others cursed.

Likewise, our global civilization will find that the reduction in the flow of oil will likewise cause a lot of gradually mounting distress until something like a forest fire comes by. It could be war, there are a lot of nukes still about. But I would lay my money (it will be worthless anyway :) on Disease. People will be hungry for awhile and the result will be that their immune systems will not be in an optimal state, then in the unsanitary conditions (no garbage collection, no sewage system) in cities especially, here and there will reappear old scourges: cholera, typhoid, plague. And some newer ones also I would bet. How to prepare for this? Well I guess knowing some basics of medicine and first aid wouldn't hurt. In fact we probably need to relearn the skills of the early 20th century illuminated by the knowledge of our own time.

26 May 2011

I was reading the Energy Bulletin and I came across an interesting article and blog on mathematical analysis of the coming Oil Crisis. I was particularly taken with an article on the Oil Shock Model. Sadly my mathematical skills are very rusty, a long time since I've done any convolution analysis. Still very interesting.

However, I wonder if all this Peak Oil analysis will miss the fact that the transition and descent will be chaotic and turbulent in the social, economic and mathematical senses of both words. Think of a turbulent little stream and throwing a leaf onto the water. You can tell how far down it will eventually go simply by the physics of gravity. But you can't describe the path. Will it get temporarily stuck in an eddy? OK, that is stretching the analogy too far, we can't get into a long lasting eddy because although the leaf doesn't need extra energy to round and round our economy does.

So what are the possible paths of transition. Let's list a few.

Smooth descent of energy usage: yeah right. We are a little more complex than bacteria in a test tube, don't expect us to go quietly into the night.

Stepped descent. This seems to be a popular idea. Energy supply drops, causes a 'bit' of a recession which results in demand destruction. The economy contracts, reduced energy demand, price of fuel drops, small growth or rather stable state. Meanwhile, the energy supply continues to decrease. Has some merit I think.

Descent causes shortages in water, food, energy. Resource wars. Bad times ensue. Probably the worst case because wars use up a lot of energy and matériel. The last thing you want to do, and a resource war would be futile, I mean what do you expect to get out a damaged country. If you can defeat them then they probably have less resources than you. Might be feasible for water since you don't need a lot of infrastructure ... just a river. Anything else requires energy / transport investment to get anything.

Nations go 'dark'. As the economy and energy distribution fail nations start to go dark. These are likely to be those with highest energy needs. This means that it would be pointless for any energy exporters to supply such nations so there will be more for others. Though how many exporters would there be when exporting nations view oil as a matter of national security? This view has been popularised by Dmitry Orlov at his blog Club Orlov.

Myself? I'm not sure. Requires more thought. As the saying goes: a trap for young players.

22 May 2011

Once upon a time I wrote the draft of a science fiction story. And I needed a way of naming stars and worlds with usable names. I came up with the idea that a survey would label promising star systems with a name based on alphabetical letters with say added bits from the Greek alphabet. The brief coding could describe a large number of instances. Seemed a good idea. But people wouldn't stick with that, they would mutate it into something usable or they would ignore it. So as a test I thought of a star with the code B - alpha - D. Convertible into a single word. But eventually the origin would be forgotten. Just as we forget the origin of the word 'Earth'. And over times words change in form. So what is this blog about? Anything I find interesting or important.

Also I tend to rant. My opinion is malleable but only with a lot of evidence.